All matter is conserved in an ecosystem, but energy flows through an ecosystem. This energy moves from one organism to the next in what is known as a food chain.
All living things need nutrients to survive, and food chains show these feeding relationships. Every ecosystem on Earth has many food chains that include a variety of organisms.
Definition of Food Chain
A food chain shows energy pathways in ecosystems. Each ecosystem on the planet has food chains of organisms ranging from producers to consumers. The producers are on the lowest level of the food chain, while the consumers that eat those producers are called primary consumers. Higher-level consumers who eat those organisms are called secondary and tertiary consumers.
You can think of a food chain as a long line that extends from producers to each consumer. Energy and nutrients move along this line in one direction.
Food Chains and Food Webs
Food chains differ from food webs in that they are showing a single line of feeding relationships. Food webs actually consist of many food chains together. A food chain is a linear display of energy movement and consumption.
On the other hand, a food web shows interrelated relationships and multiple food chains in one. Webs are a better representation of what actually happens in the real world because consumers may eat different types of producers, and more than one consumer may eat a producer.
Food webs are not linear because they show relationships among multiple trophic levels for organisms all at once. They summarize all of the food chains and relationships in an ecosystem or community. A food web reveals the different ways that plants and animals stay connected.
Definition of Trophic Levels
A trophic level is a step in the food chain that each organism occupies. In a simple food chain, it is easy to see the trophic pyramid. At the base of the food chain are the producers, and at the top of the food chain are the consumers. Each organism in a food chain represents one trophic level.
It is important to note that 90 percent of the energy is lost between each trophic level, so only 10 percent of the energy from one step is transferred to the next one. Since the energy transfer is not efficient, the size of the food chain has a limit on it. At each level, a large amount of energy is lost to heat.
General Food Chain Types
Most food chains consist of at least producers and primary consumers. Some chains are more complex and have secondary consumers and tertiary consumers. The first trophic level or first organism in a food chain usually consists of producers called autotrophs. These organisms make their own food by using light energy and turning it into chemical energy.
The second trophic level has primary consumers called heterotrophs. These organisms have to consume producers to incorporate their energy into their own biomass. They cannot make their own energy from light or chemicals.
The third trophic level has secondary consumers, which are heterotrophs that eat other consumers. The fourth trophic level has tertiary consumers or apex predators. They are high-level consumers and predators. An example of a top predator is a human who can eat both producers and other consumers.
Decomposers have their own separate trophic level and are in a different part of the food chain. They are sometimes called the last trophic level because they recycle the matter back into the soil or atmosphere. Decomposers allow producers to begin the chain again by moving nutrients and energy through an ecosystem.
Importance of Food Chains
Each organism fills a specific niche in an ecosystem that can be seen in food chains. Do they create initial energy through photosynthesis? Can they eat one group to keep the population in control? Do they decompose other organisms? Are they acting as a predator or prey?
Food chains are important because they show the intricate relationships in ecosystems. They can reveal how each organism depends on someone else for survival. Food chains also display what happens when a problem occurs and a producer or consumer is lost. Entire communities can collapse. Food chains can help scientists learn more about ecosystems and how to help them stay balanced.
Depending on the food chain you are examining, the same organism can be considered to be at more than one trophic level. For example, seals could be considered apex predators at the highest trophic level in certain environments where they eat fish that are primary or secondary consumers.
However, in other communities where seals become prey for sharks, they could be considered to be at a lower trophic level. These relationships are easier to see in food webs and harder to notice in food chains or pyramids.
Examples of Food Chains
You can find interesting examples of food chains in habitats ranging from forests to lakes. For instance, meerkats can be a top predator in one food chain by eating insects and worms. However, in other food chains, predators like eagles can eat the meerkats.
An example of a simple food chain starts with grass, which is a producer. The next level is the grasshopper or primary consumer and herbivore that eats the grass. Then, the secondary consumer is the frog that eats the grasshopper. Finally, the tertiary consumer is the hawk that eats the frog.
Another example of a food chain starts with a tree that has delicious leaves. Insects are the primary consumers that eat the leaves. Then, woodpeckers are the secondary consumers that eat the insects. Finally, a feral cat acts as the tertiary consumer and eats the woodpeckers.
Food Chain Problems
Many things can upset a food chain in an ecosystem. From natural disasters to poaching, it is possible for the careful balance of the relationships among organisms to be disturbed. If you look at the food chains that have humans at the top, pests and diseases often create problems in the food supply. This is why studying food chains is important for everyone on Earth.
For instance, as its name implies, the Colorado potato beetle eats potatoes. They can completely destroy a potato plant by consuming all the leaves and killing it. Colorado potato beetles are pests that cause serious damage to crops. In addition to attacking potatoes, they can eat tomatoes, peppers and other plants. As humans have tried to control the beetle, it has become resistant to insecticides.
The loss of producers such as potato plants is not the only problem that an ecosystem can face. The disappearance of an important consumer can also affect it. At Yellowstone National Park in the United States, the loss of wolves had a strong effect on elk populations, which exploded without the predators. The elk destroyed vegetation, including willow stands. This reduced the population of beavers that depended on the willow stands.
After the wolves were reintroduced, scientists noticed the ecosystem returning to normal at Yellowstone. Elk populations declined, vegetation increased and beavers had a food source again. This example shows how organisms depend on each other and their environments, and how a small change can upset the entire food chain or web. Sometimes the loss of a predator is as devastating as the loss of a producer.
- Khan Academy: Food Chains & Food Webs
- Study.com: What Is a Food Chain?
- National Geographic: Food Chain
- World Wildlife Fund: Food Chains and Food Webs
- Encyclopaedia Britannica: Food Chain
- BBC Bitesize KS3: Food Chains and Food Webs
- FAO: Food Chain Crisis
- MyYellowstonePark.com: Wolf Reintroduction Changes Ecosystem in Yellowstone